LONDON (Reuters) - British lawmakers took the rare step on Thursday of ordering a director of Brexit campaign group Vote Leave to parliament to answer questions about campaign spending and advertising after he refused to comply with earlier requests.

Britain's Prime Minister Theresa May addresses the House of Commons in London, March 14, 2018. Parliament TV handout via REUTERS

Dominic Cummings, former communications director of Vote Leave, has yet to appear before parliament’s culture and media committee to discuss digital advertising in the 2016 referendum campaign, despite a summons from the committee.

Whistleblowers have alleged that Vote Leave broke electoral spending law before the referendum and illegally channelled funds to a digital services firm. Vote Leave and Cummings deny the allegations.

Damian Collins, chair of the committee which is investigating the use of data and digital adverts in the referendum, brought the motion to parliament, and it was passed by the lower chamber.

“This is the first time since 1920 that a motion of this kind has been put before the House,” Collins told the House of Commons.

“It has not been done lightly, and in some ways it is done with regret.”

Cummings has until June 11 to say whether he will appear before the committee. However, while MPs backed the motion, many expressed concern that parliament was unable to force his attendance.

The episode has echoes of 2011, when Rupert Murdoch initially refused to appeared in front of MPs to discuss a newspaper phone-hacking scandal. Murdoch agreed to appear after he was issued with a summons by a parliamentary committee, before the issue was put to the House of Commons.

Collins said that Cummings was best placed to speak about allegations made against Vote Leave by other witnesses to the committee.

The committee has published a legal opinion that Vote Leave might have broken electoral spending law, and the campaign group is under investigation by the Electoral Commission.

Cummings has said he initially agreed to give evidence, and that the committee failed to agree with him on dates.

“Sending a summons is the behaviour of people looking for PR, not people looking to get to the bottom of this affair,” he said in a letter to the committee, adding in a later letter last month: “As you know, you have no powers to compel my attendance and your threats are empty.”